First principles study of bilayer graphene formed by zigzag nanoribbons

The authors investigate stability of several bilayer configurations formed by 6- and 12-zigzag graphene nanoribbons (GNR) in the framework of density function theory. Electronic structure calculations find the AB-α bilayer to be energetically preferred, and the AB-β bilayer is found to converge to the AB-α bilayer in the geometry optimisation process. Besides the AB-α bilayer, the authors find other stable bilayer configurations as local minima on the energy surface obtained by displacing the top layer relative to the bottom layer of GNR. These configurations are associated with the AB-stacking and predicted to be magnetic in nature, thus making the bilayer GNRs to be promising candidates for device applications at nanoscale.